title: PINCH1 is transcriptional regulator in podocytes that interacts with WT1 and represses podocalyxin expression.
abstract: BACKGROUND
  PINCH1, an adaptor protein containing five LIM domains, plays an important role in regulating the integrin-mediated cell adhesion, migration and epithelial-mesenchymal transition. PINCH1 is induced in the fibrotic kidney after injury, and it primarily localizes at the sites of focal adhesion. Whether it can translocate to the nucleus and directly participate in gene regulation is completely unknown.
  
  
  RESULTS
  Using cultured glomerular podocytes as a model system, we show that PINCH1 expression was induced by TGF-β1, a fibrogenic cytokine that promotes podocyte dysfunction. Interestingly, increased PINCH1 not only localized at the sites of focal adhesions, but also underwent nuclear translocation after TGF-β1 stimulation. This nuclear translocation of PINCH1 was apparently dependent on the putative nuclear export/localization signals (NES/NLS) at its C-terminus, as deletion or site-directed mutations abolished its nuclear shuttling. Co-immunoprecipitation and pull-down experiments revealed that PINCH1 interacted with Wilms tumor 1 protein (WT1), a nuclear transcription factor that is essential for regulating podocyte-specific gene expression in adult kidney. Interaction of PINCH1 and WT1 was mediated by the LIM1 domain of PINCH1 and C-terminal zinc-finger domain of WT1, which led to the suppression of the WT1-mediated podocalyxin expression in podocytes. PINCH1 also repressed podocalyxin gene transcription in a promoter-luciferase reporter assay.
  
  
  CONCLUSIONS
  These results indicate that PINCH1 can shuttle into the nucleus from cytoplasm in podocytes, wherein it interacts with WT1 and suppresses podocyte-specific gene expression. Our studies reveal a previously unrecognized, novel function of PINCH1, in which it acts as a transcriptional regulator through controlling specific gene expression.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.forename: Yingjian
authors.initials: Y
authors.lastname: Li
authors.forename: Chuanyue
authors.initials: C
authors.lastname: Wu
authors.forename: Youhua
authors.initials: Y
authors.lastname: Liu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015536:Down-Regulation / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D060588:LIM Domain Proteins; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D050199:Podocytes / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology; D025941:Protein Interaction Mapping; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D012795:Sialoglycoproteins / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D025721:WT1 Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; C088088:LIMS1 protein, human; D008565:Membrane Proteins; D012097:Repressor Proteins; D012795:Sialoglycoproteins; D025721:WT1 Proteins; C001643:podocalyxin